Okay, here we have this:
Considering the provided graph, and that a right triangle is formed, we are going to find the length of the ladder using the Pythagorean theorem, so we obtain the following:
[tex]\begin{gathered} h=\sqrt[]{4^2+2^2} \\ h=\sqrt[]{16+4} \\ h=\sqrt[]{20} \\ h\approx4.5 \end{gathered}[/tex]
Finally we obtain that the length of the ladder is approximately 4.5 meters
